Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$221.73	9.826%	$243.5172	$243.52	$243.50	$243.50
Purchase #2	$49.47	8.808%	$53.8273	$53.83	$53.85	$53.80
Purchase #3	$80.52	9.370%	$88.0647	$88.06	$88.05	$88.10
Purchase #4	$31.30	13.307%	$35.4651	$35.47	$35.45	$35.50
Purchase #5	$159.28	13.545%	$180.8545	$180.85	$180.85	$180.90
Purchase #6	$244.93	8.594%	$265.9793	$265.98	$266.00	$266.00
Purchase #7	$138.97	5.146%	$146.1214	$146.12	$146.10	$146.10
7 purchase totals =	$926.20		$1,013.8295	$1,013.83	$1,013.80	$1,013.90